Virtually all buildings and structural enclosures where human activity takes place require venting. The type of venting device employed to provide the required venting will depend on the kind of enclosure to be vented and the use to which the vented space is put. For example, bathrooms containing showers typically have active vents with fans to vent moist air and steam from the enclosed bathroom to the outdoors. Kitchens, particularly in restaurants and hotels, similarly have powered vents for removing cooking by-products such as smoke and steam to the outdoors.
Other types of enclosures, such as attics, do not require active venting. However, such enclosures do typically require a passive venting device to allow for air flow from the enclosure to the outdoors. Such venting is required, for example, to prevent a buildup of moisture in the enclosure. Rather than forcing air out of the enclosure, passive venting devices typically include a vent structure in the form of upstanding walls defining an aperture to allow airflow between the interior of the enclosure and the exterior of the building or structure. Passive venting devices can also include a screen to block animals, insects and other unwanted objects from entering the enclosure through the opening.
Passive venting devices are well-known and have been extensively used in the past. Notably, many jurisdictions have building codes that require passive venting devices for venting attic spaces. House attics and other similar enclosures are sometimes vented simply by one or more passive venting devices on the roof. The passive venting devices are each positioned above a ventilation passage or opening in the roof which permits air to flow from the building enclosure to the outside, and vice versa.
However, in addition to permitting air to flow from the building enclosure to the outside though the roof opening, prior art roof vents also tend to allow moisture to enter the building enclosure from the outside, which can cause damage to the building or structure and fosters growth of mold and mildew which can lead to health problems for occupants.
U.S. Pat. No. 6,767,281 to McKee discloses one prior art passive venting device that attempts to prevent precipitation from entering the building enclosure from the outside. The McKee venting device, which is a common passive venting device used to vent building enclosures, comprises a base member, including an attachment portion and a vent structure for permitting gas and vapour to pass through the device, a cover member mounted to the base member so as to permit the flow of gas and vapour to the outside, and a precipitation baffle which is sized, shaped and positioned to interfere with the entry of precipitation to the outside. The device also has a ventilation pathway spaced from the roof so as to permit thick shakes or tiles to be installed right up to the device without interfering with ventilation.
While the McKee venting device, and others like it are formed with a base having an aperture and a cover, and are generally effective at preventing moisture from entering the enclosure therethrough, there is room for improvement.
For example, during periods of heavy rain, the falling rain will hit the roof with sufficient force to bounce under the covers of prior art venting devices, and through their apertures into the enclosures they are venting. Heavy precipitation can also result in a flow of water along the slope of a roof which splashes and sprays when it encounters a prior art roof vent. The splash and spray from the flow of water against the prior art roof vent can also work its way under its cover and through its aperture into the enclosure. A steeply sloped roof can make this situation worse since water will naturally flow down a steeply sloped roof at a greater velocity as compared to a roof having a moderate slope or no slope at all. In addition to heavy precipitation, snow and ice melting on a roof may also lead to a flow of water along the slope of the roof.
U.S. Pat. No. 6,520,852, also to McKee, discloses another passive vent for venting a building enclosure which attempts to prevent splashing and spraying caused by the flow of water down a sloped roof with an upstanding portion having a peak on one side which helps to deflect the water flow around the venting device. However, providing a peak on the upstanding portion of the passive vent, or other irregular shapes, creates the potential for other problems, such as for example, over-cutting shingles to match the outline of the roof vent, creating holes for water to gain pathways into the shingles to the roof surface underneath, and into the roof opening bypassing the roof vent altogether.
Providing passive vent devices with other irregular shapes, for example to accommodate attachment parts, especially parts positioned along sides of the venting device, also makes it difficult or inconvenient to install shingles right up against the vent structure. This results in a space between the contours of the vent structure of the vent device and the shingles, permitting water to work its way under the shingles from the side, which is yet another way in which moisture can enter a building enclosure, essentially bypassing the roof vent.
Another attempt for dealing with heavy water flows on sloped roofs is disclosed in U.S. Pat. No. 3,093,059 to Metz. Metz discloses a roof ventilator with removable hood wherein the hood presents an apron section which slopes downwardly and rearwardly and terminates in a rearwardly directed tongue lying parallel with and in touching contact with a base plate. In heavy rain, the sloped apron of the hood will allow the flow of water to run over the top of the hood covering a collar which is in communication with the ventilation opening in the roof. However, since the collar is positioned forwardly of the sloped apron section, moisture is still liable to work its way through the collar and into the ventilation opening of the Metz roof ventilator.
Yet another attempt at reducing water entry into passive venting devices is shown in U.S. Pat. Application No. 2007/0049190 filed by Singh. Singh discloses a protective barrier adapted to fit over a conventional roof vent, particularly an off-ridge roof vent, which provides for ventilation and also restricts the passthrough of wind driven rainwater. The off-ridge roof vent comprises a top having an inflection, a front lip, two openings covered by screen mesh, and an interior entrance into an attic space. The off-ridge roof vent, which lacks a separate base portion for attachment to the roof, is positioned over the interior entrance into an attic space between the upslope side and the inflection. However, the lack of a separate base makes attaching and sealing the off-ridge roof vent to the roof more difficult.
Other prior art patents of general interest in the field of passive venting devices include U.S. Pat. No. 3,094,915 to Leigh, U.S. Pat. No. 3,579,930 to Murphy, U.S. Pat. No. 3,895,467 to Clement, U.S. Pat. No. 4,184,414 to Jarnot, U.S. Pat. No. 4,297,818 to Anderson, U.S. Pat. No. 4,759,270 to Linden, U.S. Pat. No. 4,899,505 to Williamson, U.S. Pat. No. 5,664,375 to Ward, U.S. Pat. No. 6,293,862 to Jafine, U.S. Pat. No. 6,612,924 to Mantyla, U.S. Pat. No. 6,520,852 to McKee, U.S. Pat. No. 6,733,381 to Ploeger, U.S. Pat. No. D304,367 to Saas, U.S. Pat. No. D376,007 to Thomas, and U.S. Pat. No. D556,314 to Daniels.
Another way in which moisture can enter a building enclosure through prior art passive roof venting devices is through condensation that accumulates inside the venting device, typically under the cover, as a result of a temperature difference between the venting device and the air flowing therethrough. The condensed moisture often collects on the underside surface of the cover of the prior art roof vents and drips down through the opening into the building enclosure.
While attempts have been made by others at directing water about the exterior of venting devices and other devices, none have dealt with the problem of how to prevent moisture condensing on an interior of a passive venting device and dripping into the enclosure.